The present invention relates capacitance type sensors and to the conversion of the variable capacitance of the sensor to a digital value.
Capacitance sensors have found a wide range of applications. Capacitance sensors are used for sensing pressure, acceleration, flow, humidity, proximity, angle, rotation, as well as human interface sensing applications. For example, capacitance sensors are used for differential pressure measurement as well as absolute pressure measurement.
The variable capacitance produced by a capacitance sensor must be converted to an electrical signal that can be processed to produce a measurement output. In many cases, it is desirable to produce the electrical signal as a digital value that represents the variable capacitance, so that further signal processing can be done with digital circuitry rather than analog circuitry.
Capacitance-to-digital (C/D) converters using sigma delta modulators have been used in conjunction with capacitance sensors. One example is the use of sigma delta modulators for C/D conversion is in conjunction with capacitance pressure sensors.